Allow inlining after errors

But avoid inlining:

 - if the typechecking the body to inline generated errors
 - if checking inlined method generated errors
 - if we are in an inline typer and the same inline typer
   already generated errors.

Author: odersky

compiler/src/dotty/tools/dotc/typer/Inliner.scala

@@ -37,7 +37,9 @@ object Inliner {
   def hasBodyToInline(sym: SymDenotation)(implicit ctx: Context): Boolean =
     sym.isInlineMethod && sym.hasAnnotation(defn.BodyAnnot)
 
-  /** The body to inline for method `sym`.
+  /** The body to inline for method `sym`, or `EmptyTree` if none exists.
+   *  Note: definitions coming from Scala2x class files might be `@forceInline`,
+   *  but still lack that body.
    *  @pre  hasBodyToInline(sym)
    */
   def bodyToInline(sym: SymDenotation)(implicit ctx: Context): Tree =
@@ -48,7 +50,7 @@ object Inliner {
 
   /** Should call to method `meth` be inlined in this context? */
   def isInlineable(meth: Symbol)(implicit ctx: Context): Boolean =
-    meth.is(Inline) && hasBodyToInline(meth) && !ctx.inInlineMethod
+    meth.is(Inline) && !ctx.inInlineMethod && !bodyToInline(meth).isEmpty
 
   /** Should call be inlined in this context? */
   def isInlineable(tree: Tree)(implicit ctx: Context): Boolean = tree match {
@@ -108,8 +110,7 @@ object Inliner {
       cpy.Block(tree)(bindings.toList, inlineCall(tree1))
     else if (enclosingInlineds.length < ctx.settings.XmaxInlines.value) {
       val body = bodyToInline(tree.symbol) // can typecheck the tree and thereby produce errors
-      if (ctx.reporter.hasErrors) tree
-      else new Inliner(tree, body).inlined(tree.sourcePos)
+      new Inliner(tree, body).inlined(tree.sourcePos)
     }
     else
       errorTree(
@@ -424,7 +425,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
     // Compute bindings for all this-proxies, appending them to bindingsBuf
     computeThisBindings()
 
-    val inlineTyper = new InlineTyper
+    val inlineTyper = new InlineTyper(ctx.reporter.errorCount)
 
     val inlineCtx = inlineContext(call).fresh.setTyper(inlineTyper).setNewScope
 
@@ -991,7 +992,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
    *  4. Make sure inlined code is type-correct.
    *  5. Make sure that the tree's typing is idempotent (so that future -Ycheck passes succeed)
    */
-  class InlineTyper extends ReTyper {
+  class InlineTyper(initialErrorCount: Int) extends ReTyper {
     import reducer._
 
     override def ensureAccessible(tpe: Type, superAccess: Boolean, pos: SourcePosition)(implicit ctx: Context): Type = {
@@ -1038,7 +1039,11 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
 
     override def typedApply(tree: untpd.Apply, pt: Type)(implicit ctx: Context): Tree = {
       constToLiteral(betaReduce(super.typedApply(tree, pt))) match {
-        case res: Apply if res.symbol == defn.InternalQuoted_exprSplice && level == 0 && call.symbol.is(Macro) =>
+        case res: Apply
+        if res.symbol == defn.InternalQuoted_exprSplice &&
+           level == 0 &&
+           call.symbol.is(Macro) &&
+           !suppressInline =>
           expandMacro(res.args.head, tree.span)
         case res => res
       }
@@ -1088,7 +1093,11 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
         }
       }
 
-    override def newLikeThis: Typer = new InlineTyper
+    override def newLikeThis: Typer = new InlineTyper(initialErrorCount)
+
+    /** Suppress further inlining if this inline typer has already issued errors */
+    override def suppressInline given (ctx: Context) =
+      ctx.reporter.errorCount > initialErrorCount || super.suppressInline
   }
 
   /** Drop any side-effect-free bindings that are unused in expansion or other reachable bindings.

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -806,8 +806,6 @@ class Namer { typer: Typer =>
 
     private def addInlineInfo(sym: Symbol) = original match {
       case original: untpd.DefDef if sym.isInlineMethod =>
-        if (sym.owner.isClass && sym.owner.seesOpaques)
-          ctx.error(em"Implementation restriction: No inline methods allowed where opaque type aliases are in scope", sym.sourcePos)
         PrepareInlineable.registerInlineInfo(
             sym,
             implicit ctx => typedAheadExpr(original).asInstanceOf[tpd.DefDef].rhs

compiler/src/dotty/tools/dotc/typer/PrepareInlineable.scala

@@ -222,42 +222,43 @@ object PrepareInlineable {
           val inlineCtx = ctx
           inlined.updateAnnotation(LazyBodyAnnotation { _ =>
             implicit val ctx = inlineCtx
-            val rawBody = treeExpr(ctx)
-            val typedBody =
-              if (ctx.reporter.hasErrors) rawBody
-              else ctx.compilationUnit.inlineAccessors.makeInlineable(rawBody)
-            checkInlineMethod(inlined, typedBody)
-            val inlineableBody = typedBody
-            inlining.println(i"Body to inline for $inlined: $inlineableBody")
-            inlineableBody
+            val initialErrorCount = ctx.reporter.errorCount
+            var inlinedBody = treeExpr(ctx)
+            if (ctx.reporter.errorCount == initialErrorCount) {
+              inlinedBody = ctx.compilationUnit.inlineAccessors.makeInlineable(inlinedBody)
+              checkInlineMethod(inlined, inlinedBody)
+              if (ctx.reporter.errorCount != initialErrorCount)
+                inlinedBody = EmptyTree
+            }
+            inlining.println(i"Body to inline for $inlined: $inlinedBody")
+            inlinedBody
           })
         }
     }
   }
 
   def checkInlineMethod(inlined: Symbol, body: Tree)(implicit ctx: Context): Unit = {
+    if (inlined.owner.isClass && inlined.owner.seesOpaques)
+      ctx.error(em"Implementation restriction: No inline methods allowed where opaque type aliases are in scope", inlined.sourcePos)
     if (ctx.outer.inInlineMethod)
       ctx.error(ex"implementation restriction: nested inline methods are not supported", inlined.sourcePos)
     if (inlined.name.isUnapplyName && tupleArgs(body).isEmpty)
       ctx.warning(
         em"inline unapply method can be rewritten only if its right hand side is a tuple (e1, ..., eN)",
         body.sourcePos)
-  }
+    if (inlined.is(Macro) && !ctx.isAfterTyper) {
 
-  def checkInlineMacro(sym: Symbol, rhs: Tree, pos: SourcePosition)(implicit ctx: Context) = {
-    if (sym.is(Macro) && !ctx.isAfterTyper) {
-      def isValidMacro(tree: Tree)(implicit ctx: Context): Unit = tree match {
+      def checkMacro(tree: Tree): Unit = tree match {
         case Spliced(code) =>
           if (code.symbol.flags.is(Inline))
             ctx.error("Macro cannot be implemented with an `inline` method", code.sourcePos)
           Splicer.checkValidMacroBody(code)
-          new PCPCheckAndHeal(freshStagingContext).transform(rhs) // Ignore output, only check PCP
-
-        case Block(List(stat), Literal(Constants.Constant(()))) => isValidMacro(stat)
-        case Block(Nil, expr) => isValidMacro(expr)
-        case Typed(expr, _) => isValidMacro(expr)
+          new PCPCheckAndHeal(freshStagingContext).transform(body) // Ignore output, only check PCP
+        case Block(List(stat), Literal(Constants.Constant(()))) => checkMacro(stat)
+        case Block(Nil, expr) => checkMacro(expr)
+        case Typed(expr, _) => checkMacro(expr)
         case Block(DefDef(nme.ANON_FUN, _, _, _, _) :: Nil, Closure(_, fn, _)) if fn.symbol.info.isImplicitMethod =>
-          // TODO Suppot this pattern
+          // TODO Support this pattern
           ctx.error(
             """Macros using a return type of the form `foo(): given X => Y` are not yet supported.
               |
@@ -272,10 +273,9 @@ object PrepareInlineable {
               |
               | * The contents of the splice must call a static method
               | * All arguments must be quoted or inline
-            """.stripMargin, pos)
+            """.stripMargin, inlined.sourcePos)
       }
-      isValidMacro(rhs)
+      checkMacro(body)
     }
   }
-
 }

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -111,6 +111,7 @@ class Typer extends Namer
    */
   private[this] var foundUnderScala2: Type = NoType
 
+  // Overridden in derived typers
   def newLikeThis: Typer = new Typer
 
   /** Find the type of an identifier with given `name` in given context `ctx`.
@@ -1601,10 +1602,8 @@ class Typer extends Namer
     if (sym.isInlineMethod) rhsCtx.addMode(Mode.InlineableBody)
     val rhs1 = typedExpr(ddef.rhs, tpt1.tpe.widenExpr)(rhsCtx)
 
-    if (sym.isInlineMethod) {
-      PrepareInlineable.checkInlineMacro(sym, rhs1, ddef.sourcePos)
+    if (sym.isInlineMethod)
       PrepareInlineable.registerInlineInfo(sym, _ => rhs1)
-    }
 
     if (sym.isConstructor && !sym.isPrimaryConstructor) {
       for (param <- tparams1 ::: vparamss1.flatten)
@@ -2734,10 +2733,11 @@ class Typer extends Namer
       }
       else if (Inliner.isInlineable(tree) &&
                !ctx.settings.YnoInline.value &&
-               !ctx.isAfterTyper &&
-               !ctx.reporter.hasErrors) {
+               !suppressInline) {
         tree.tpe <:< wildApprox(pt)
-        readaptSimplified(Inliner.inlineCall(tree))
+        val errorCount = ctx.reporter.errorCount
+        val inlined = Inliner.inlineCall(tree)
+        if (errorCount == ctx.reporter.errorCount) readaptSimplified(inlined) else inlined
       }
       else if (tree.symbol.isScala2Macro) {
         if (tree.symbol eq defn.StringContext_f) {
@@ -3047,6 +3047,9 @@ class Typer extends Namer
     }
   }
 
+  // Overridden in InlineTyper
+  def suppressInline given (ctx: Context): Boolean = ctx.isAfterTyper
+
   /** Does the "contextuality" of the method type `methType` match the one of the prototype `pt`?
    *  This is the case if
    *   - both are contextual, or

tests/neg/GenericNumLits/Test_2.scala

@@ -2,4 +2,5 @@ object Test extends App {
 
   val e1: Even = 1234
   val e2: Even = 123  // error: 123 is odd
+  val e3: Even = 123456789101111 // error: number too large
 }